Berlin 2012 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 27: Transport and Anomalous Diffusion
DY 27.7: Vortrag
Donnerstag, 29. März 2012, 16:15–16:30, MA 004
Simulation of colloids in microchannels: channel width effects on diffusion — •Ullrich Siems and Peter Nielaba — Department of Physics, University of Konstanz, 78457 Konstanz, Germany
The results of a Brownian dynamics simulations (BD) of colloidal particles in a two-dimensional microchannel are presented. The particles pair potential is modeled by a repulsive 1/r3 potential and a hard core interaction. The diffusion along the channel direction is investigated for various channel widths at a constant interaction strength. For channels, where the mutual passing of particles is forbidden due to the hard core interaction, single-file diffusion has been observed in agreement with former simulations and experiments.
For wider channels a three regime diffusion behavior can be observed: the diffusion is normal in the short-time limit and long-time limit, but sub-diffusive on intermediate time scales. The time evolution of the mean square displacement can be completely characterized by the two transition times and the diffusion coefficients for the short-time and the long-time limit. These parameters were obtained by a fit of a Fermi distribution to the logarithmic coordinates of the time-dependent diffusion coefficient D(t)=<Δ x2>/2t. The transition times and the long-time diffusion coefficient have an oscillating dependency on the channel width, which can be explained by layering effects.